This investigation is concerned with the immunogenicity of liposomal model membranes in mice and other species. The liposomes are prepared from mixtures of an appropriate phospholipid, sterol, and charged amphiphile, and are rendered immunogenic by incorporation of a suitable synthetic amino-substituted phosphatidylethanolamine (PE) derivative. They differ significantly from conventional immunogens in which a hapten is covalently attached to a macromolecule (e.g. protein) since, in liposomes, the hapten (i.e. PE derivative) is inserted noncovalently into lipid bilayers which function as carrier. Thus, liposomes constitute a unique experimental tool for studying the influence of a number of key parameters on an immune response. This property derives from the fact that such variables as, for example, density, number, and type of determinant, as well as the chemical environment, can be simply regulated by varying the composition of the lipid mixture used to generate the model membranes. BIBLIOGRAPHIC REFERENCES: Yasuda, T., G.F. Dancey, and S.C. Kinsky. (1977). "Immunogenicity of liposomal model membranes in mice: dependence on phospholipid composition." Proc. Nat. Acad. Sci. U.S. 74, 1234-1236. Daney, G.F., T. Yasuda, and S.C. Kinsky. (1977). "Lipid A enhancement of liposomal model membrane immunogenicity." Federation Proceedings 36, 1321 (abstract).